Tool Path Research Articles

Effect of tool path strategy and tooltip profile on geometrical feature and surface quality of Al-6061 alloy during deformation machining in bending mode

ABSTRACT Deformation machining (DM), a hybrid manufacturing process, involves subtractive manufacturing and the incremental forming process. This hybridisation of manufacturing technologies produces monolithic components having complex profiles and reduces raw material wastage. In this work, the influence of different toolpath methods, approaches, and design of the tool on the geometrical features and surface quality of the fin formed through the bending mode of the DM process was investigated for aluminium alloy Al-6061 T6. Different combinations of straight and curved fin toolpath techniques with top-to-bottom and bottom-to-top approaches were investigated to bend the machined fin in the desired shape. Thereafter, different tool profiles were explored with the bottom-to-top approach and curved toolpath strategy. The fabricated fin was 3D scanned to evaluate the geometrical features, and the surface roughness was also measured. The better quality of the formed components in terms of geometrical features and surface roughness was identified with the optimal combination of the tool profile and toolpath strategy, i.e. tool profile T3 has a circular sector and nose radius of 0.5 mm, curved toolpath method, and bottom-to-top approach. This optimal combination was further utilised to analyse the forming forces during the bending mode of the DM process.

Optimisation of tool path shape in trochoidal milling using B-spline curves

In recent years, trochoidal milling has become greatly widespread since it provides high productivity and long tool life, especially when cutting difficult-to-machine materials. Numerous studies have dealt with the analytical description and the experimental investigation of the evolution of cutting force, temperature, tool wear, chatter stability, etc. However, most of these analyses are focusing on the conventional circular and cycloid-shape trajectories. Only a few studies address the potential of improving the efficiency by modifying the tool path shape, leaving significant reserves untapped. If the mathematical formulation of the trajectory cannot be described easily, then a sophisticated optimisation algorithm is needed to determine the appropriate tool path shape. To overcome these difficulties at trochoidal milling of straight slots, the present work proposes a new tool path generation algorithm that can maximize the average material removal rate (MRR) while controlling the tool load. In this approach, the tool path is modelled by a B-spline curve whose control points are optimised using a differential evolution algorithm. The developed tool path generation strategy was compared through simulations and experiments with two widely used solutions viz the traditional cycloid-shaped tool path and a modern approach used in computer-aided manufacturing (CAM) systems. The results reveal that the developed method is able to control the tool load and the smoothness of the tool path, and most importantly, also exceeds the existing methods in terms of productivity.

Autonomous Robotic Sensing for Simultaneous Geometric and Volumetric Inspection of Free-Form Parts

Robotic sensing is used in many sectors to improve the inspection of large and/or complex parts, enhancing data acquisition speed, part coverage and inspection reliability. Several automated or semi-automated solutions have been proposed to enable the automated deployment of specific types of sensors. The trajectory to be followed by a robotic manipulator is typically obtained through the offline programmed tool paths for the inspection of a part. This method is acceptable for a part with known geometry in a well-structured and controlled environment. The part undergoing assessment needs to be precisely registered with respect to the robot reference system. It implies the need for a setup preparation phase for each new part, which can be very laborious and reliant on the human experience. This work combines real-time robot control and live sensor data to confer full autonomy to robotic sensing applications. It presents a novel framework that enables fully autonomous single-pass geometric and volumetric inspection of complex parts using one single robotised sensor. A practical and robust robot control sequence allows the autonomous correction of the sensor orientation and position to maximise the sensor signal amplitude. It is accompanied by an autonomous in-process path planning method, capable of keeping the inspection resolution uniform throughout the full extension of the free-form parts. Last but not least, a by-product of the framework is the progressive construction of the digital model of the part surface throughout the inspection process. The introduced framework is scalable and applicable to widely different fields.

Integrated Interface System of STEP Data Models for the Tool Path Generation

The STEP (STandard for the Exchange of Product model data) is a worldwide standard for exchanging products between diverse computer systems and industrial applications. STEP files (ISO 10303) contain 3D data in the universal data format with a boundary representation (B-rep) that allows the exchange of data models between CAD, CAM, and CNC systems. Traditionally, G-code generation relies on CAM software as an add-on, which incurs significant installation costs. The purpose of this paper is to describe the development of an Integrated Interface System (I2S) for Tool Path Generation (TPG) for the CNC milling operations utilizing neutral STEP files.The algorithm was interpreted in Hypertext Preprocessor (PHP) programming and produced a computer interface system that is capable to convert STEP file geometric data to G-code format.The geometric features of the sample block were modeled using a 3D CAD model. The result was validated using machining simulation, and the machining is performed on a three-axis CNC milling machine with a PC-based controller.In modern manufacturing systems based on Open Architecture Controller (OAC), the development of the I2S provides an alternative to generating machining tool paths and G-code by intercepting CAM software.

Application of CAD/CAM Technology in Electrochemical Relief Design and Processing of Ceramic Art

Ceramic relief modeling design and CNC machining programming have a wide range of applications in industrial production and daily life. In view of the actual needs of enterprises, this research studies the CAD simulation technology of ceramic relief and achieves the modeling of other pieces of relief based on the geometric outline of the plane breakthrough. According to geometric relief modeling, bitmap relief modeling, tool path selection, and relief simulation processing, the establishment of a ceramic relief model is realized. Finally, the simulation processing is carried out on the ArtCAM software platform, and reasonable processing parameters are obtained to realize the CNC engraving processing of ceramic relief. The experimental results show that the machining efficiency of the ceramic relief model established in this study is improved by 11.3% and 42.8%, respectively, compared with the two traditional methods, which verifies the correctness and superiority of the designed model.

A knowledge-based method for tool path planning of large-sized parts

Proper tool paths ensure the high-efficiency and high-quality machining of workpiece. The current tool path planning method is inadequate to meet the complex process requirements for the complex workpiece of abundant local features. Due to the lack of ability of independent process decision-making, the planning effect is still heavily dependent on human experience and the planning is time-consuming and laborious, which is not conducive to shortening development cycle of new products. Therefore, a novel knowledge-based method for tool path planning is proposed in this paper. The proposed method can automatically plan the tool path that meets the requirements of the machining process by the adaptive process decision-making according to the perceived features of complex workpiece. The knowledge extraction method based on the syntactic dependency analysis is used to extract named entities in the process document. And the correctly classified entities are filled in the nodes of knowledge model represented by the form of frame to finish the establishment of process knowledge base. Then, with the help of feature extraction module based on the hybrid clustering method, the semantic segmentation of the point cloud of the workpiece is completed, and the Feature Matrix (FM) is formed. This matrix is used to provide feature information required for process decision, including Feature Vector (FV) and Structure Description Matrix (SDM). Finally, the tool path is generated in the Path Generator. At last, an automatic path planning system is developed for the painting process of automotive exterior. The planned paths are tested for 20 types of bumpers, where the chromatic aberration ΔE of each product is less than 1.4; both the average thickness of each paint and the requirement of production rate are satisfactory. These test results verify the effectiveness of the proposed tool path planning method.

GA-based time-optimal feedrate scheduling on NURBS tool path with geometric and drive constraints

GA-based time-optimal feedrate scheduling on NURBS tool path with geometric and drive constraints

Dynamic modeling of milling and effect of tool path on machining stability

Dynamic modeling of milling and effect of tool path on machining stability

Kinematics of a 5-axis hybrid robot near singular configurations

• A method based on kinematics modification for singularity avoidance is proposed. • A criterion for choosing the appropriate inverse kinematic solution is presented. • A semi-analytical algorithm for forward kinematic analysis is developed. • An algorithm is developed by modifying C -axis instructions. • Both simulations and experiments are carried out to verify the proposed approach. This paper proposes a method for non-singular tool path generation based on inverse kinematics modification in joint space to deal with the singularity problem of a 5-axis hybrid robot in machining process. Firstly, a criterion for choosing the appropriate solution of inverse displacement analysis is presented, that enables the avoidance of mechanical interference and enlargement of the task workspace. As a counterpart of inverse displacement analysis, a semi-analytical algorithm for forward displacement analysis is developed with high computational efficiency. These works lay a comprehensive and solid foundation for motion control and tool path simulation of the hybrid robot. Then, it reveals that at a singular configuration that varies with the system configurations, sudden changes occur in both rotation of the C -axis of the 2-DOF wrist and lengths of three telescopic legs within the 3-DOF parallel mechanism. This finding leads to an effective method for non-singular tool path planning by directly modifying the C -axis commands in the joint space using linear interpolation technique. Finally, both simulation and experimental results on a prototype machine show that in the neighborhood of singularity, continuous and smooth joint motions and acceptable tracking accuracy can be ensured after the modification.

Some applications of optimization routing problems with additional constraints

The paper deals with an extremal routing problem with constraints. In the general formulation, it is assumed that the objects of visiting are any non-empty finite sets — megalopolises. The main applied problem considered in this study is the tool path optimization problem for CNC sheet-cutting machines, known as the Cutting Path Problem. This problem arises at the stage of developing control programs for CNC machines. Other applications are also possible. In particular, the results obtained in the chapter can be used in the problem of minimizing the radiation dose when dismantling a system of radiation-hazardous elements after accidents at nuclear power plants and in transport problems. Among tasks constraints, the precedence constraints are investigated. These constraints can be used to reduce computational complexity. As the main method, the study used broadly understood dynamic programming. The offered realization of the method takes into account the precedence constraints and the dependence of the objective functions on the task list. This dependence belongs to the class of very complex conditions that determine the route admissibility at each routing step, depending on the tasks already completed or, on the contrary, not yet completed. As applied to the Cutting Path Problem, the dependence of the objective function on the task list makes it possible to reduce thermal deformations of the material during cutting. The chapter provides a mathematical formalization of an extremal routing problem with additional constraints, a description of the method, and the exact algorithm obtained with its help. The order of task execution, the specific trajectory of the process, and the starting point are optimized.

In-situ 4-point flexural testing and synchrotron micro X-ray computed tomography of 3D printed hierarchical-porous ultra-high temperature ceramic

3D printed ceramics have received much attention of late due to the ability to manufacture complex near net shapes with a range of structures across multiple length scales. The introduction of hierarchical features offers a wider array of properties, yet with this comes additional unknowns as to their limits including the mechanisms behind failures. The present work applies in-situ Synchrotron micro X-ray computed tomography (μXCT) with 4-point flexural testing to study and further understand the failure pattern of 3D printed hierarchical porous ultra-high temperature ceramics. Samples were imaged at incremental load steps to observe the propagation of defects until final failure, where in the case of the strain tolerant logpile structure a full crack spanning the height and width of the sample was captured and reconstructed revealing a complex tortuous fracture path. The relative strength and density of the structures are related to the sintered microstructure and the printed logpile or honeycomb geometry, which are described using Gibson’s and Ashby’s theory for brittle foams. In addition, tomographic data was used to extract detailed information on porosity and material density distribution within honeycomb and logpile 3D printed lattice structures that was related to the tool path planning of each layer. • First capture and tomographic reconstruction of complex fracture path in 3D printed UHTC logpile lattice structure. • Synchrotron μXCT of honeycomb and logpile lattice structures provided detailed density information. • Relative strength and density were related to microstructure and the 3D printed logpile/honeycomb internal lattice structure. • Logpile structures exhibited tortuous fracture path and resulted in greater strain tolerance compared to honeycomb.

Numerical modeling and experimental evaluation of machining parameters for 2-dimensions ultrasonic-assisted micro-milling at low and high-speed machining

Vibration assisted machining (VAM) is one of the hybrid machining processes for improving the machined surface quality. VAM performance is mainly influenced by the combination of machining and vibration control parameters, where surface roughness value (Ra) became the benchmarking indicator. It is difficult to determine the optimum parameter combination to produce high precision products, especially for micro-milling, due to the interconnected correlation among parameters. The benefits of high-speed machining with VAM are high material removal rate and shorter machining time than low-speed machining. VAM operation at high-speed machining is still limited due to the high possibility of chatter occurrence. Therefore, this research aims to evaluate the 2D VAM resonant performance at low-speed and high-speed machining, operated at ultrasonic vibration and amplitude below one μm. The mathematical model and experimental evaluate the vibration effect based on machining mode, amplitude, and spindle speed variation. The mathematical modelling and experiment result complement each other, where the mathematical model can characterize the effect of resonant vibration, amplitude, and spindle speed increment on the tool path trajectory. The 2D resonant vibration at the feed direction causes interrupting cutting and transforms the tool path trajectory from linear to wavy. The mathematical model and experiment result show the dominant influence of spindle speed and feed rate on the toolpath trajectory and Ra, where low spindle speed and feed rate result in better machine surface roughness. The low-speed machining with VAM results in Ra value between 0.1–0.155 μm, which is below the high-speed machining result, between 0.2–0.38 μm

Tool-path planning method for kinematics optimization of blade machining on five-axis machine tool

Planning tool paths on free-form surfaces is a widely discussed issue. However, satisfying all the requirements of blade machining using traditional path-planning methods remains a challenge. Herein, a new iso-parametric path-planning strategy, based on a novel parameterization method and combined with conformal transformation theory, is proposed. The presented strategy adapts to the curvature of blade surfaces, improving the kinematic performance of the machining process, reducing the complexity of multi-axis coordinated motion control, and improving the machining quality. A comparison between the proposed and three traditional methods is also discussed. The influence of the tool path on the kinematic performance of the machine tool is quantitatively examined based on the kinematic models of two different machines. Finally, the results of a deep-cutting milling experiment conducted to verify the improvement of the machining quality due to kinematic optimization are described. The proposed method provides a more reasonable path-planning approach for blade machining on a five-axis machine tool, which can significantly reduce the cost of blade machining, minimize the risks of blade failure, and enhance the large-scale automated production of blades.

An Approach for Predicting Stiffness of a 5-DOF Hybrid Robot for Friction Stir Welding

This paper presents an approach for stiffness identification of a 5-DOF hybrid robot named TriMule for friction stir welding. The novelty of this approach is to visualize the realistic robotic system that considers the elastic deflections of all joints and links as a fictitious robotic system that only considers the elastic deflections of joints along their axes. Thus the number of parameters to be identified is reduced significantly. The stiffness identification is essentially implemented by the following four steps: (1) formulating the Cartesian stiffness model that maps the joint compliances of the fictitious system to the deflection twist of the end-effector, (2) parameterizing the joint compliances by a set of polynomial functions in terms of nominal actuated joint variables, (3) constructing the multiple linear regression equations by projecting the measured elastic deflections from the operational space onto the joint space, and (4) estimating the polynomial coefficients by robust biased estimation. The stiffness identification experiment and offline compensation experiment for the tool path deviations are carried out on a prototype machine to demonstrate the effectiveness of the proposed approach.

Finite Element Simplifications and Simulation Reliability in Single Point Incremental Forming.

Single point incremental forming (SPIF) is one of the most promising technologies for the manufacturing of sheet metal prototypes and parts in small quantities. Similar to other forming processes, the design of the SPIF process is a demanding task. Nowadays, the design process is usually performed using numerical simulations and virtual models. The modelling of the SPIF process faces several challenges, including extremely long computational times caused by long tool paths and the complexity of the problem. Path determination is also a demanding task. This paper presents a finite element (FE) analysis of an incrementally formed truncated pyramid compared to experimental validation. Focus was placed on a possible simplification of the FE process modelling and its impact on the reliability of the results obtained, especially on the geometric accuracy of the part and bottom pillowing effect. The FE modelling of SPIF process was performed with the software ABAQUS, while the experiment was performed on a conventional milling machine. Low-carbon steel DC04 was used. The results confirm that by implementing mass scaling and/or time scaling, the required calculation time can be significantly reduced without substantially affecting the pillowing accuracy. An innovative artificial neural network (ANN) approach was selected to find the optimal values of mesh size and mass scaling in term of minimal bottom pillowing error. However, care should be taken when increasing the element size, as it has a significant impact on the pillow effect at the bottom of the formed part. In the range of selected mass scaling and element size, the smallest geometrical error regarding the experimental part was obtained by mass scaling of 19.01 and tool velocity of 16.49 m/s at the mesh size of 1 × 1 mm. The obtained results enable significant reduction of the computational time and can be applied in the future for other incrementally formed shapes as well.

Comparison of laser deposition methods for the synthesis of AlxCoCrFeNi multi-principal element alloy

Additive manufacturing (AM) of multi-principal element alloys (MPEAs) has enabled high throughput synthesis for rapid alloy design and development for targeted structural properties. However, the complex solidification cycles endured by the material during processing often yield disparate outcomes when porting the processing conditions between different laser deposition techniques. With difference in the cooling rates being a primary difference between laser metal deposition (LMD) and powder bed fusion (PBF), understanding the effects of the processing on the microstructures and material properties is critical to assess the printability of such complex alloys. Here, we compare the fabricability, quality, and structural properties of AlxCoCrFeNi MPEA synthesized by LMD and PBF. Our results indicate that the equiatomic MPEA processed using PBF exhibits interfacial cracks due to warping and bending between successive deposit layers, while the LMD produces crack free near-dense deposits. XRD characterization corroborates a relatively high lattice strain of 1.8 × 10−3 in the PBF sample resulting from the high residual stresses arising from the relatively high cooling rates (∼106 K/s) during the processing. While the PBF sample assumes smaller grains relative to the LMD processed alloy, no significant differences are noted in the crystallographic phases of the alloys produced by the two approaches. Also, the tool path employed to fabricate the alloy by LMD can facilitate gradation in the structural properties driven by the variation in thermal gradient during the synthesis. Further, we propose methods to map material space while porting processes within AM, enabling fabricability of alloys using PBF and DED.

Surgical GAN: Towards real-time path planning for passive flexible tools in endovascular surgeries

Automatic surgical path planning of the passive flexible tool encounters a prohibitive challenge, typically in endovascular surgery (ES). The key problem is that unstructured surgical environment and tools’ unpredictable motion is hard to be explicitly modeled. We propose a generative adversarial networks (GAN)-based framework (defined as surgical GAN) towards automatic guidewire path planning in real time for ES. A novel GAN architecture is proposed by combining convolutional neural networks (CNN) and long short-term memory networks (LSTM), which extracts and fuses the spatial features in medical images and temporal features of historical tool path as the conditional information. It inputs the surgical state information and continuously outputs the local future path of the guidewire tip. A training dataset (3.5*105 samples) is collected under laboratory conditions with 10 surgeons. Effects of different CNN architectures and path planning length on network performance are investigated. User experiments, with the tasks delivering the guidewire tip inside a vascular model (endovascular evaluator) from the aortic arch into the left common carotid artery (LCCA), left subclavian artery (LSCA), or brachiocephalic trunk, are conducted with 10 novice surgeons in an operating room. The results shows significant improvement of a path planning accuracy with surgical GAN compared with baseline networks (from 46.2%–69.78%) and the non-rigid registration method (72.94%). Results of user experiments demonstrate an overall better task performance with the guidance of planned surgical path. Collectively, surgical GAN can achieve real-time path planning of the guidewire in simulated ES, and holds great potential for novice training and robotic ES autonomy.

Development of a Novel Approach to Predict Tool Life Based on Tool Path Features in Ta6V Milling

Abstract In the manufacturing industry, titanium alloys machining has always been a challenge, mostly because of tool premature wear. Consequently, the understanding of physical phenomena and their modeling have become critical research topics for productivity improvement. The majority of tool wear model is based on cutting condition variations. However, several tool paths with the same cutting conditions lead to different tool lives. The impact of the cutting strategy is significant on tool wear and complex to anticipate. In this article, a global method allowing to estimate the impact of a cutting strategy on tool life is presented. It is based on tool path features extracted from workshop cutting power signals collection. First, optimal cutting conditions are determined according to AFNOR standard by minimizing specific cutting coefficient. Then, correlation analysis is carried out for different configurations of the database. Special iconography of correlations is used to explain links between the features. To finish, from the correlations between impact of the tool path on tool life and the features, a multiple regression model based on the method of least squares is computed to estimate the impact of the tool path on tool life. Physical correlations have been highlighted and confirmed the significant role of the cutting strategy on tool life. Models are quite accurate despite the low amount of data and the method is promising for an industrial implementation.

Numerical study on the effect of oscillation on the deformation behavior of single point incremental formed part

The paper reports the deformation behavior of single point incremental formed part with sheet oscillation. Single point incremental forming is an emerging manufacturing technology. This technology provides the competition to the other innovative technologies such as electric-assisted manufacturing, hydroforming, high-speed forming, etc., to produce the lightweight and highly deformed components. Single point incremental forming is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any processing time to undergo plastic deformation. In single point incremental forming, the part stays fixed and the tool pin makes the planar and downward motion to shape the part. It has several advantages over the conventional process such as high process flexibility, elimination of die, complex shape, and better formability. Previous literature provides enormous research on the formability of metal during this process, process with various metals and hybrid metals, the influence of various process parameters, but research on the deformation behavior of the part through the oscillation of the tool was limited. In this paper, the single point incremental forming was simulated on ABAQUS finite-element software. The spiral tool path was studied. First, the part was formed without oscillation. Then the oscillation of the sheet with the help of a die and blank holder was set with a frequency to deform the part. The variation of frequency and amplitude was also studied. The formability of the part was analyzed and compared. The deformation, profile shape, strain path, thickness, and force requirement were analyzed and presented. It was found that with lower cycles the maximum stress increases with an increase in amplitude. Also, with an increase in the number of cycles the achieved strain values were lower as compared to the no oscillation case for the same cup height and thus higher deformation is possible with oscillation.

Minimizing the energy consumption of hole machining integrating the optimization of tool path and cutting parameters on CNC machines

Minimizing the energy consumption of hole machining integrating the optimization of tool path and cutting parameters on CNC machines